no regex here

def is_phone_number(text): # test program to find U.S. phone numbers in a string
    if text[0].isdecimal():
        if len(text) != 12:
            return False # not the right length
        for i, char in enumerate(text):
            if i == 3 or i == 7:
                if char != "-":
                    return False # index not hyphen
            elif not char.isdecimal():
                return False # index is not integer
        return True # string matches general criteria for a U.S. phone number
    if text[0] == "(":
        if len(text) != 14:
            return False
        for i, char in enumerate(text):
            if i == 0:
                if char != "(":
                    return False # index is not bracket
            elif i == 4:
                if char != ")":
                    return False # index is not bracket
            elif i == 5:
                if char != " ":
                    return False # index is not whitespace
            elif i == 9:
                if char != "-":
                    return False # index is not hyphen
            elif not char.isdecimal():
                return False # index is not integer
        return True # string matches general criteria for a U.S. phone number

message = "Call me at 415-555-1345 this afternoon, or tomorrow at (415) 555-3612 for my office line."

found_number = False

for i in range(len(message)):
    chunk = message[i:i+12]# takes a chunk of 12 characters out of the string, shifting by one character each time
    if is_phone_number(chunk):
        print(f"Found phone number {chunk} in the message.")
        found_number = True
    chunk2 = message[i:i+14]# takes a chunk of 12 characters out of the string, shifting by one character each time
    if is_phone_number(chunk2):
        print(f"Found phone number {chunk2} in the message.")
        found_number = True
if not found_number:
    print("Could not find any phone numbers in the string.")